Configuring the Bridge
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3.5.2Destination Indexes 0 and 254:DynamicMessageRouting
The bridge providesameansfordynamicrouting ofmessagesatruntime.
Dynamicrouting appliesonlytomessagesinitiated fromTCP/IPhosts,and
requiresthe host toconfigurethe bridge atruntime(toDestination Index255).
Youshould be aware ofyouroptionsforusing dynamicrouting inyourapplication,
as you setup yourmapped routings.TwoDestinationIndexesarereserved for
routing messagesdynamically:0 and 254 decimal.Youroptionsare:
HDestination Index 0:Host--basedrouting AModbusPlusroutingpathis
availableinthe bridge atindexlocation0for runtime use byTCP/IPhosts.
When the hostconfiguresa pathinthe bridge,anymessage fromthathost
addressed toindex0will be routed tothatModbusPluspath.The bridge
maintainsacache ofup to 10 associationsbetween TCP/IPhostsand
ModbusPluspaths.
Thisrouting option allowsthe bridge tobeconfigured forsimple addressing
toModbusPlusfromTCP/IPnodeswhich do notsupportgatewayrouting.
HDestination Index 254:Socket--basedrouting AModbusPlusrouting
pathisavailableinthe bridge atindexlocation 254 forthe currentTCP/IP
hostconnection only.Thebridge maintainsone socketconnection at that
indexlocation foreach ofitseightProgramand eightData paths.
Thisrouting option allowsthe bridge to handleconcurrentsessionsfromone
TCP/IPhost, orfrom multiple hosts,using independentrouting assignments.
It providesflexibilityforyourapplication tomanage routing dynamically,in
addition tothe bridge’sfixed mapping table.
Section 3.9 providesexamplesofdynamicrouting.
3.5.3Destination Index 255:BridgeInternalCommand
Messagesreceived bythe bridge addressed toDestination Index255 causethe
bridge to executeaninternaloperation.Thisindexisused toconfigurethe bridge
fordynamicrouting,ortoinvoke an upload ordownload operation between the
hostand bridge.
Section 3.9 providesexamplesofdynamicrouting.Sections5.2 and 5.3 provide
examplesofuploading and downloading.
3.5.4ReservedDestination Indexes
Destination Indexes250 ... 253 arereserved and are notavailableforuse.